Method of manufacturing metallic magnesium



May 30, 1944. T. ARMOR. ETAL 2,349,927

METHOD MANUFACTURING METALLIC` MAGNESIUM Filed April 22, 1941 MAGNESITE CALCIUM cARsmE Mg CO5) Ca Ca L RoAsTlNG REnucme msrlLLATloN 3 FIRSTSTEP SECONDSTEP T MAGNESLA (Mg o) nouBLE nEcoMPosmoN r r r DEfOMPOITlON REBIDUE HABNESIUM CHI-WIDE SOLUTION REDUCUN RESIDUE METALLIC MAGNESUM (Ca'COa) (BNQ Claaqa (Cu Fa) (Mg) THIRD STEP DOUBLE DECOMDOSITIONI INVENTORS: Tswlosm HRlMoRI yum@ KoNlsHr JuNmcm )smansm RmNosum: YosHlMuRH Patented @dit 1i NBTEIRENG'METALLC Custodian Application April 22, 1941, Serial No. 389,728

(ci. 'z5-67) '7 Claims. The present invention relates to'a method of manufacturing metallic magnesium, which consists in double-decomposing the calcium uoridecontaining residue produced,v in manufacturing metallic magnesium by heating magnesium uoride and calcium carbide. with magnesium salt solution having the acid radical that does not produce insoluble precipitates with lime, such as magnesium chloride and magnesium nitrate; providing the thus-separated magnesium fluoride as a reducible material using calcium carbide, while the mother liquor, namely, water-soluble salt of magnesium and lime is mixed with the roasted product of the initial material, magnesite or dolomite and is heated and caused to react, passing carbonio acid gas therethrough, the lime being precipitated as carbonate, while the magnesium salt solution is double-decomposed with the calcium iluorde-containing residuey obtained as a' lay-product in the reaction of magnesium fluoride y,with calcium carbide and thus is converted to magnesium fluoride to `be used as a reducible material. The object thereof is to obtain metallic magnesium of high purity very economically from magnesium-containing ores and calcium carbide by employing intermediate products a cyclically through all the stages o! the operation.

Thereis known a method oi obtaining metallic magnesium of high purity from magnesium and silicon-containing ores such as magnesite or dolomite by manufacturing nagnesiuml iluoride, mixing calcium carbide'therewith intimately, reducing the mixture by heating it at above 750 C.

vunder reduced pressure or in the presence of a reducing 'gas under the normal or reduced pressure so as to produce magnesium vapor and then l condensing the said magnesium vapor.

This invention has improved the above known method, in which the calcium iluoride-containing residue produced by the rea'ction of magnesium fluoride with calcium carbide is converted into hydrofluoric acid and gypsum by being actedI upon by sulphuric acid, and by treating magnesiacontaining ores with the former, magnesium fluoride is manufactured. However, such method has the disadvantage of not alone employing undesirable hydrofiuoric acid, but also consuming a large quantity of sulphuric acid. This invention has been completed as the result of diligent study regarding a process for recovering iluorine veryefl'ectively by treating the calcium fluoride-containing residue obtained as a byproduct in the reaction of magnesium fluoride with calcium carbide, at the same time manufacturlng magnesium fluoride from\magnesia containing ores easily. Especially, we have found that the magnesium fluoride produced in this invention is in small particles and possesses great 4reactivity when it is caused to react in a solid condition with calcium carbide, so that it is possible to produce magnesium vapor in a short time. 1

To make it easy to explain the present invention, let us begin with themanufacture of the various intermediate products necessary to start the operation. Firstly, prepare concentrated solution of magnesium salts having-r the acidic radical that does not produce insoluble precipitates with lime, such as magnesium nitrate or magnesium chloride obtained by dissolvingmagf nesia in nitric acid'or hydrochloric acid, etc. Next, after adding an excess of the above solution to a ilnely-pulverized uoride (preferably, the solution of about 2-chemical equivalents against calcium fluoride), subject the mixture to heattreatment, so that by double-decomposition it may be converted into the precipitate of magnesium fluoride and decomposition mother liquor (mixed solution of calcium salt and magnesium salt). 'Ihe .thus-obtained magnesium fluoride and decomposition mother liquor are only,l the intermediate products primarily necessary to start this operation. In practice and in a con- 1 tinuous operation these intermediate products are Vthis invention divided into three steps of operation:

In the flrst step, rstly, very active magnesia is manufactured by roasting magnesia-contain-v ing ores such as magnesite anddolomite. and is thrown into the above decomposition mother liquor prepared for the starting of the operation` (mixed solution of calcium salt and magnesium salt. Subsequently the decomposition motherl liquor produced inV the third step `described hereafteris used.) Next, carbonic acid gas is introduced thereinto, so that magnesia may be converted by double-decomposition into concentrated solution oi' magnesium salts having the acidic radical that does not produce insoluble precipitates lwith lime, such as magnesium nitrate. magnesium chloride, etc., and the lime is precipitated'as calcium carbonate.v Now, if -the above reaction is shown by.a chemical equation, taking magnesium chloride as a magnesium salt having the acidic radical that does not produce insoluble precipitates with lime, it is as follows (as the similar explanation may bc given regarding the other magnesium salts, no explanation will be given hereafter regarding chloride):

MgO-l-CaClz-tMgClzl-COz=CaCO3|2MgCl2 (l) (Solution) (Solution) (lrecipitatc) (Solution) By the way, in this reaction the impurities present in the magnesia-containing ores and decomposition mother liquor, suchas silicio acid, alumina, iron oxide, lime, etc. are not only all removed together with the precipitate of calcium carbonate, but also the chlorine in the decomposition mother liduorremployed is wholly recovered and it is possible to prepare magnesium chloride solution of high purity from magnesiacontaining-ores such as magnesite and dolomite.

The concentrated solution of magnesium chloride obtained in this step is used in the third step described hereafter.

Next, in the second step, mixing calcium carbide intimately with the magnesium fluoride prepared as above (subsequently the magnesium fluoride recovered and regenerated in the third step is employed), the mixture is reduced by heating it to above 750 C. under reduced pressure or in the presence of a reducing gas under the normal or reduced pressure so as to separate it into magnesium vapor and a calcium fluoridecontaining substance, this reaction being shown by the following equation:

The magnesium vapor reduced and distilled here is condensed and solidified and recovered as metallic magnesium of high purity, while the reaction residue is provided for the following third step.

In the third step. after adding an excess of the concentrated solution of magnesium chloride prepared in the first step (preferably, about two chemical equivalents against the calcium fluoride contained in the reduction residue) to the said reduction residue consisting chiefly of calcium' iiuoride which has been produced in the second step, the mixture is double-'decomposed by heating and converted into the precipitate of magnesium fluoride and decomposition mother liquor containing calcium chloride and magnesium chloride, the reaction in this third step being as shown by the following equation:

Calif -l- QML'FIQ MUFQ -I- Fam? -l- Mcm? (3 (Precipitate) 'l (Solution) Precpitntc) (Solution) (Salut i011 That is to say. by this step it is possible to recover completely the fluorine containedin the reduction residue obtained in the second step, as magnesium fluoride of high purity. The thusobtained magnesium fluoridev isl a small and in homogeneous particles and has a considerably different physical property from that of the magnesium fluoride produced by reacting hydrofluoric acid upon powdered magnesite or lightly roasted magnesia. It is very quick in the speed of reaction with the said calcium carbide in the second step. The above reduction residue often containing considerable quantities of calcium carbide, lime, magnesia, etc., hinders the reaction of the third step, but these may be removed easily by washing the residue previously with dilute acid. i

If the Equationsv (l), (2) and (Il) in the rst, secondand third steps are combined, thc following equation 1sobta1ned:

MgO+CO2+CaCg=Mg+CaCO3-l-2C v(Il) In this way, according to the present invention the various materials employed intermediately are all recovered and utilized cyclically with good effect by the combination of all the steps and very pure metallic magnesium can-be manu- 5 factured from magnesium-containing ores and calcium carbide only.

in short, this invention has rationalized the known method of obtaining metallic magnesium by using magnesium-containing ores such as magnesite and dolomite as the material and manufacturing magnesium fluoride as an intermediate product and reducing the same with calcium carbide. as the various materials used intermediately can. be circulated effectively, 'the invention can be carried out very economically. Moreover, the magnesium fluoride obtained by this invention possesses great reactivity with calcium carbide and is very quick in the speed ci the reaction. The following is an example of performing this invention:

The analysis table of the materials used in this example, magnesite and calcium carbide, is as follows:

Magnesite (produced in Daisekkyo, Manchurla) Per cent Magnesia 46.20

Lime 0.54

Alumina and iron oxide 9.78 Silica 3.26

Loss on ignition 48.97

Calcium carbide (commercial) Calcium carbide 72.5 Lime 14.5

Silica 3.4 Alumina and iron oxide 3.0

Others 6.6

. Frasi' STEP Firstly, put 80.5 litres of the decomposition Imother liquor (containing 9.0 kilograms of magnesium chloride and 10.4 kilograms of calcium chloride) obtained in the above third step of the circulating continuous operation, into a closed vessel, and after the addition of the active magnesia obtained by roasting 9.0 kilograms ofmagnesite powder having the above-mentioned constituents at '700 C., pass carbonio acid gas through it at approximately 80` C. while stirring it. Then, double-decomposition will be completed very easily, precipitating calcium carbonate. Next, filter and wash the said calcium carbonate, .and 98.5 litres of magnesium chloride solution almost free from lime (containing 17.7 kilograms of magnesium chloride and 0.08 kiloygrams of calcium chloride) will be obtained. The pure magnesium chloride thus regenerated and (l0 recovered is provided directly for the Third step described hereafter.

SECOND STEP If 6.3 kilograms of the magnesium fluoridev of lime, the rest being alumina, iron oxide, silica, calcium carbide and magnesia) are obtained.

Metallic magnesium Per cent Purity 99.98

impurities: y

Silicon 0.005 Iron c- 0.003 Aluminium e 0.004

The reduction residue produced here is provided directly for the following Third step.

THIRD Sres If the reduction residue obtained in the above second step is made into a muddy state by adding about 20 litres of waterand lthen dilute hydrochloric acid is added While stirring the above residue. the calcium carbide, lime and other lnjurious matters contained in the residue are dissolved easily. Filter'them. Next, after adding 98.5 litres of the magnesium chloride solution 'regenerated in the first step to this purified residue, double-decompose the mixture'l by heating and extract the thus-produced decomposition matter with warm water, while the precipi.

tate produced is filtered and washed. Next, if this precipitate is roasted at a low temperature, 6.3 kilograms of magnesium fluoride (purity, 96.02%) and 83 Alitres ofy decompositionmother liquor (containing 8.91 kilograms of magnesium chloride and 10.34 kilograms of calcium chloride) are obtained. Such regenerated magnesium iluoride and decomposition mother liquor are repeatedly employed cyclically for the next Second step and the regeneration of the magnesium chloride solution of the next First step respectively. Further, the acid washed waste liquor obtained as a by-product `in this step (containing chielly calcium chloride) may be utilized for the preparation of magnesium chloride solution of high purity by the similar treatment to that given to the said decomposition mother liquor.

As will be seen from the above example, the

yield of metallic magnesium in the Second step is about 80%, and if allrthe steps are combined,

.nearly '76% of the magnesium contained in the- 4 initial material,l magnesite, can be.. recovered as metallic magnesium of high purity. However,-

the above is only one example and it is possible to raise the yield and purity ofmetallic inag-l nesium by the proper selection of the operating condition of4 each step, material, etc'.

` We claim:

1. The method of recovering metallic magnesium which consists in roasting a magnesium ore,

carbon dioxide into the solution, treating the resulting magnesium salt solution with calcium fluoride, returning the liquor to the calcium salt solution, distilling the residual magnesium fluoride with calcium carbide to vaporize metallic magnesium, and returning the calcium nuorlde residue tothe magnesium salt solution.

3. The method of recovering metallic magnesium which consists in roasting dolomite, suspending it in a solution of a calcium salt, passing carbon dioxide' into the solution, treating the resulting magnesium salt solution with 'calcium fluoride, returning the liquor to the calcium salt solution, distilling the residual magnesium nuoride with calcium carbide to vaporize metallic magnesium, and returning the calcium fluoride residue to the magnesium salt solution.

4. The method of recovering metallic magnesium, which consists in roasting a magnesium ore, suspending it in a solution of calcium chloride. passing carbon dioxide into the solution, treating the resulting magnesium chloride solution with calcium fluoride, returning the liquor to the calcium chloride solution, and dlstiliing the residual magnesium fluoride with calcium carbide to vaporize metallic magnesium, and returning the calcium uoride residue to the magnesium chloride solution.

5. The method of recovering metallic magnesium, which consists in roasting a magnesium ore, suspending it in a solution of calcium nitrate, passing carbon dioxide into the solution, treating the resulting magnesium nitrate solution with calcium fluoride, returning the liquor to the calcium nitrate solution, and dlstilling the residual magnesium iiuoride with calcium carbide to vaporize metallic magnesium, and returning the calcium fluoride residue to the magnesium nitrate solution.

6. The method of recovering metallic magnesium which consists in roasting a magnesium ore, suspending it in a solution qt a calcium salt, passing carbon dioxide into the solution, treating the resulting magnesium salt solution with calcium fluoride, returning the liquor'to the calcium salt solution, distilling the residual magnesium fluoride with calcium carbide to vaporize metallic magnesium, removing impurities from the calcium fluoride residue by solution in acid and returning the purified calcium fluoride to the magnesium salt solution.

7. The method of recovering metallic magnesium which consists in roasting a magnesium ore, suspending it in a solution of a calcium salt, passing carbon dioxide into the solution, treating the resulting magnesium salt solution with an amount of calcium fluoride insuflicient to satisfy all of the magnesium salt present, return ing the liquor containing the excess magnesium salt to the calcium salt solution, distilling the residual magnesium fluoride with calcium carbide to vaporize metallic magnesium andreturning the calcium fluoride residue to the magnesium salt solution.

TSUYOSHI ARIMORI.

YUKIO KONISHI.

. JUNUCHI ISHIBASHI.

RINNOSUKE YOSHIMURA. 

